If you know anything about dental disease, then you know bacteria ranks high on the Usual Suspects list. Tooth decay gets its start from acid produced by bacteria; periodontal (gum) disease is often triggered by bacteria that infect the gums.

But the particular strains of bacteria that can cause dental disease are a small percentage of the 10,000-plus species inhabiting your mouth. The rest, numbering in the millions, are fairly benign—and some, as recent research is now showing, play a sizeable role in protecting your teeth and gums against other malicious bacteria, fungi and viruses.

Dr. Aaron Weinberg, a dental researcher at Case Western Reserve University, has been investigating these protective bacteria for many years. His research began with a scientific conundrum: although the mouth has one of the highest densities of bacterial populations, wounds in the mouth tend to heal quickly.

The answer, he believes, originates with human beta defensins (hBDs), substances produced by cells in the lining of the mouth that are natural antibiotics against disease. He has found that certain bacteria actually help stimulate their production.

This isn't just an interesting fact about the body's defenses and immune system. During his research, Dr. Weinberg was able to identify the agent within the bacteria that triggered hBD production. This has opened up a new line of research: The possibility that harnessing this agent might help assist in our treatment of infection by boosting the body's defensive capabilities.

For example, researchers have proposed including a form of the agent in toothpaste. Over time, this might stimulate hBD production and guard the mouth against the development of dental diseases like gum disease.

These possibilities all come from our increasing knowledge and understanding of the microscopic world around us, especially in our mouths. Bacteria are much more complex than we may have realized—not all are our enemies, and some are definitely our friends. Learning more may open up new ways to keep our teeth and gums healthy.